High voltage circuit breaker supported on a base isolating tripod for earthquake protection
DOI:
https://doi.org/10.5459/bnzsee.22.3.145-154Abstract
The 1987 Bay of Plenty earthquake caused the total destruction of a 220 kV circuit breaker. Failures occurred in the porcelain columns supporting the Interrupter Heads.
There are many other circuit breakers of the same type in the national grid. To protect these circuit breakers from earthquake damage, a proposal is made to replace the existing support stand with a base isolating tripod.
On the tripod, Helical Springs and oil filled dampers are used to control the earthquake induced motion of the circuit breaker. By controlling this motion the forces on the porcelain support column are reduced to a safe level.
The design is modelled using a multi degree of freedom system subjected to Response Spectrum and Time History analyses. The model produces results which are consistent with tests, and confirms the design parameters selected by a single degree of freedom approximation.
The result is an economical tripod stand design which is expected to protect the circuit breaker from earthquake ground accelerations up to twice the level of the 1940 El Centro earthquake. This level of earthquake is considerably stronger than the 1987 Bay of Plenty earthquake.
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